A hybrid mode-locked Er-doped fiber laser based on single-walled carbon nanotube saturable absorber and nonlinear amplifying loop mirror (NALM) is constructed. At 1564.5 nm, the mode-locked laser is self-started by carefully adjusting the polarization controller, with the repetition frequency of 16.24 MHz, 3-dB spectral width of 8.5 nm and pulse width of 302 fs. Compared with the laser only utilizing single-wall carbon nanotube saturable absorber or NALM mode-locked Er-doped fiber laser, the hybrid one has narrower output pulse width and the mode-locking state is more stable.
Known as a unique optical filter, Faraday anomalous dispersion optical filter has prior advantages to provide high transmission and high background noise rejection with excellent image quality. In this paper, we studied the temperature characteristics of Faraday anomalous dispersion optical filter at Cs 852 nm transition. The transmitted spectrum is carefully measured under different Cs cell temperatures (39°C–57°C) and environment temperatures (23°C–26°C). The results could provide important reference for further research on Faraday laser, lidar remote sensing systems and imaging systems.
The continuously bandwidth-tunable pulse generation in the SWNT mode-locked fiber laser is achieved by only tuning the intracavity polarization state. By introducing the in-line polarizer with 2-meter-long polarization maintaining fiber pigtails in a typical ring fiber laser, a bandwidth-tunable SWNT mode-locked fiber laser is constructed. The mode locker is the single-wall carbon nanotube saturable absorber, which is fabricated by optical deposition in the ~0.27 w.t % ultrasonic carbon nanotube alcohol solution. By only tuning the intracavity polarization controllers, the spectral bandwidth is continuously tuned in the range of 0.94 to 3.04 nm. We attribute the upper limit of the spectral bandwidth to the limit of the free spectral range determined by Lyot filter, which consists of polarization controllers and in-linepolarizer in the cavity. These results provide a simple way to achieve bandwidth-tunable subpicosecond pulse, which should be attractive to the applications requiring ultrafast sources with tunable bandwidth or pulsewidth.
Terahertz dual-comb spectroscopy (THz-DCS) has the potential to be used as universal THz spectroscopy with high spectral resolution, high spectral accuracy, and broad spectral coverage; however, the requirement for dual stabilized femtosecond lasers hampers its versatility due to the bulky size, high complexity, and high cost. We here report the first demonstration of dual THz comb spectroscopy using a single free-running fiber laser. While greatly reducing the size, complexity, and cost of the laser source, THz-DCS maintains the spectroscopic performance comparable to a system equipped with dual stabilized fiber lasers, and can be effectively applied to gas spectroscopy.